1. Field of the Invention
This invention relates to knives that have thin replaceable blades with an innermost blade of a stack of blades being able to protrude from the housing of the knife.
2. Description of the Related Art
There is substantial prior art in the designing of utility knives that include a quantity of stored blades. The knife can be activated to release a dull blade which will then permit insertion of a separate sharp blade in a usable position. In the past, the mechanical structure that is used to cause protruding of a blade that is to be used has not been designed well enough to make the operation of the extending and retracting of the blade and removing and dispensing of the used blade with replacement of a new blade in such a manner that permits ease of operation. Also, such utility knives of the prior art have not been designed in a manner that facilitates the maximizing of the size of the blade storage chamber within the knife in order to increase the number of stored blades within the knife.
A basic embodiment of utility knife where the innermost blade is to be extendable from a stored stack of blades which utilizes a housing having an internal chamber. A blade track is mounted within the internal chamber. A blade carrier is mounted within the blade track. The blade carrier is movable in a linear direction between an extended position and a retracted position. The blade carrier is to contain a single blade (the innermost blade) with this blade to protrude from the housing when the blade carrier is in the extended position. A thumb button is connected to the blade carrier with the thumb button to be slidingly movable to cause the blade carrier to move between the retracted position and the extended position. An engaging block is mounted on the blade carrier with the engaging block being movable between an engaging position and a non-engaging position. With the engaging block in the engaging position, a single blade, which comprises the innermost blade of the stack of blades, is engaged by the engaging block and is movable along with the blade carrier between the extended position and the retracted position. A pair of mounting pins are mounted on the blade carrier. The engaging block is movably mounted on the mounting pins. The engaging block being biased by a single spring toward the engaging position. A release button is mounted on the housing. Pressing of the release button when the blade carrier is in the extended position will cause the engaging block to be moved against the spring that connects with the engaging block to move the engaging block to the non-engaging position which will permit extraction of the dull innermost blade from the housing and replacement of that blade by a new sharp innermost blade.
A further embodiment of the present invention is where the basic embodiment is modified by a line connecting between the mounting pins being not in alignment with the linear direction. This misalignment of the mounting pins prevents the engaging block from canting relative to the blade carrier so as to be movable smoothly and evenly by the spring relative to the blade carrier to insure that the engaging block will properly engage with the innermost blade.
A further embodiment of the present invention is where the basic embodiment is modified by the thumb button having an inner portion with the inner portion being mounted within a receiving chamber formed in the blade carrier. The inner portion is laterally displaced from the outer portion of the thumb button in order to maximize the space within the blade storage chamber.